Part of it is lighting, part of it is parameters, such as the material’s glossiness. Your export settings from MegaScans might not be calibrated to UE4 either.
Also, I recommend modifying your textures A LOT if you’re going to use MegaScans. People will recognize those textures from that library easily and it’s always better to add your own touch to these things anyhow.
Edit: Also looked at your material graph. It looks like you’re doubling up on maps. Do you understand PBR? You only need the roughness map, and you can plug in a constant 0 for metalness since that texture doesn’t contain any.